1. Field of the Invention
The present invention relates to a metal or resin tube joint used for water pipes and the like.
2. Description of the Related Art
FIG. 5 shows one example of a tube joint for jointing ends of axially opposed metal or resin tubes 1, 1 such that extending and contracting function and flexible function are provided. The tube joint includes a joint body 2 and a pair of push rings 3 and 3, and they are fastened by fastening means 4 which are T-shaped bolts and nuts. The joint body 2 includes opposed flange-like projections 2a and 2a, and a cylindrical barrel portion 2b which is integrally formed such as to swell between the projections 2a, 2a. Each of the projections 2a is provided at its inner periphery with a receiving port 2c whose diameter becomes wider toward its end. The push ring 3 also includes a projection 3a, the joint body 2 is located at the outer periphery between the joint tubes 1 and 1 while leaving a circumferential gap, and the push rings 3, 3 are disposed at the opposite ends, and the ends are fastened by the fastening tools 4. By fastening using the fastening tools 4, a rubber packing 5 set between the joint body 2 and each of the push rings 3 is pushed by surfaces of the push rings 3 and connected to the receiving port 2c in wedge form, and is also contacted to an outer peripheral surface of the joint tube 1 under pressure. With this, watertightness is established so that liquid flowing through the joint tubes 1, 1 should not leak outside.
As shown in FIG. 5 also, the conventional tube joint has a structure that if the fastening tools 4 are fastening, the rubber packing 5 can freely be fastened. Therefore, even if a tolerance fastening torque is indicated, the fastening state varies depending upon operators, and torque can not be controlled.
The cross section of the rubber packing 5 (JIS K6353; A type) shown in FIG. 5 is tapered, and any portions thereof are relatively hard, and homogeneous having the same resilience. Therefore, strong pressing force can not be obtained, and the sealing ability is not sufficient. As a rubber packing which can be used in the tube joint shown in FIG. 5, there exists one having soft portion (JIS K6353; K type), but a volume of the rubber packing occupied by the soft portion is smaller than that occupied by the hard portion, and there is a room for improvement of the resiliently deforming and sealing abilities.